Some may call it chance, but Verna DeSpain is convinced fate led school bus mechanic Thomas Mitchell to her doorstep last week.The mechanic from Clarksville, Tennessee, fills in as a substitute bus driver for the Clarksville-Montgomery County School System (CMCSS) when he’s needed. His route occasionally includes bringing a group of special needs children to school.That’s when he first met DeSpain and her 10-year-old daughter, Lydia, a third-grader who uses a wheelchair. One morning, Mitchell noticed DeSpain, a single mother of two, struggling to carry Lydia’s wheelchair down the steps of their front porch. For some reason, he just couldn’t shake the image from his head.“There was just hardly any room for her to maneuver this wheelchair,” Mitchell told the school district, which posted the story on Facebook. “It just didn’t seem right for somebody to have to struggle like that.”So, a few days later, he gave DeSpain a call and …READ MORE ON CBSNEWS.COM